MONDAY, Oct. 24 (HealthDay News) -- Myopia, or nearsightedness, is much more common among children and teenagers today than it was about 40 years ago, but spending more time outside could help reverse this trend, a new study suggests.

The authors argued that increased exposure to natural light and more time spent looking at objects from afar might protect kids' vision.

British researchers analyzed data from eight previous studies on outdoor time in 10,400 children and teens with myopia. For every hour spent outside each week, the odds that a child would develop myopia dropped by about 2%.

The finding are slated for presentation Monday at the annual meeting of the American Academy of Ophthalmology, held in Orlando, Fla.

In the study, nearsighted children spent nearly four hours less time outside weekly, on average, than other kids with normal vision or farsightedness. The protective effect is linked to just being outside, not engaging in specific activities, the researchers said in an academy news release.

They added that more research is needed to determine if there is also a link between "near work" such as playing computer games or studying and the increase in myopia among kids. Whether increasing the amount of time kids with myopia spend outside will prevent their nearsightedness from getting worse is another topic for consideration, the researchers said.

"Increasing children's outdoor time could be a simple and cost-effective measure, with important benefits for their vision and general health," study author Dr. Anthony Khawaja, of the University of Cambridge, said in the release. "If we want to make clear recommendations, however, we'll need more precise data. Future, prospective studies will help us understand which factors, such as increased use of distance vision, reduced use of near vision, natural ultraviolet light exposure or physical activity, are most important."

Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.